1. Field of the Invention
The present invention relates to a base station, a mobile station, a mobile communication system, and a method of controlling control signal transmission.
2. Description of the Related Art
In W-CDMA (Wideband-CDMA) and HSDPA (High-Speed Downlink Packet Access), an enhanced technology of W-CDMA, for example, a base station transmits to a mobile station a data information signal, and an upper-layer control signal (e.g., user information, user authentication, and a control signal for handover when a user moves from one cell to another).
In W-CDMA, in downlink, dedicated channels allocating a specific code to a certain user and a shared channel shared by all users are provided. A base station multiplexes transmission data of each channel in code domain (see e.g., Non-Patent Document 1). Specifically, a base station includes a Forward Access Channel (FACH) and a Broadcast Channel.
The FACH, a channel for multiplexing control information of each user on a time axis, is used mainly for exchanging an upper layer signal at the time of a call setup. This signal is mapped onto a Secondary Common Control Channel in physical layer. For example, the FACH is used in a Random Access Channel response. A Broadcast Channel is a channel for reporting broadcast information common to all users (e.g., system information, or cell information). These signals are mapped onto a Primary Common Control Channel.
Moreover, in W-CDMA, in an uplink channel, a base station uses a Random Access Channel. The Random Access Channel is a channel for transmitting upper-layer control information. The control information is mapped onto a Physical Random Channel.
On the other hand, in HSPDA, in a downlink, HS-SCCH (High Speed Shared Control Channel) and HS-PDSCH (High Speed Physical Downlink Shared Channel) are added to W-CDMA.
HS-SCCH conducts, in a Shared CH, Layers 1 and 2 signalling at the time of HS-PDSCH transmission for high-speed packet transmission. Information transmitted using this HS-SCCH, including user information and MCS (Modulation & Coding scheme Set), are code-multiplexed with a HS-PDSCH.
HS-DPCCH conducts, in a dedicated CH, Layers 1 and 2 signalling at the time of receiving HS-PDSCH for high-speed packet transmission. Information transmitted using this HS-DPCCH, an ARQ (Automatic Repeat Request) ACK/NACK and a CQI (Channel Quality Indicator), are code-multiplexed (see e.g., Non-Patent Document 1).
Non-Patent Document 1
3GPP TS 25.212
Non-Patent Document 2
3GPP TS 25.213